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URL: https://oeis.org/A308766

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A308766
Numbers k such that the minimal mark in a length k sparse ruler is round(sqrt(9 + 12*k)/2) + 1.
6
51, 59, 69, 113, 124, 125, 135, 136, 139, 149, 150, 151, 164, 165, 166, 179, 180, 181, 195, 196, 199, 209, 210, 211
OFFSET
1,1
COMMENTS
Other sparse rulers in the range length 1 to 213 have round(sqrt(9 + 12*k)/2) minimal marks.
Minimal vertices in k-edge graceful graph = minimal marks in length k sparse ruler.
Minimal marks can be derived from A004137 and using zero-count values in A103300.
Conjecture: Minimal marks k - round(sqrt(9 + 12*k)/2) is always 0 or 1.
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Ed Pegg Jr, Jun 23 2019
STATUS
approved